Circuit interrupter trip contact resetting means



Jan. 27, 1970 wAsAauRo MURAI ETAL 3,492,609

CIRCUIT INTERRUPTER TRIP CONTACT RESETTING MEANSv s sheets-Sheet 1' Filed Jan. 22, 1968 ATTORNEYS Jan. 27, 1970 wAsABuRo MURAI ETA'L 3,492,609

CIRCUIT INTERRUPTER TRIP CONTACT RESETTING MEANS Filed Jan. 22. 196e 5 Sheets-Sheet 2 l l I l l l l I I v f INVENT ORS WSABURO MURAI YUJIRO YASOJIMA ATTORNEYS FIGLB Jan. 27, 1970. wAsAauRo MURA1. ETA'- 3,492,609

CIRCUIT INTERRUPTER TRIP CONTACT RESETTING MEANS 3 Sheets-Sheet 3 Filed Jan.

S Rl OA R MU M WO YUJIRO YASOJ IMA ATTORNEYS United States Patent C) 3,492,609 CIRCUIT INTERRUPTER TRIP CONTACT RESETTING MEANS Wasaburo Murai and Yujiro Yasojima, Osaka, Japan, as-

signors to Terasaki Denki Sangyo Kabushiki Kaisha,

Osaka, Japan Filed Jan. 22, 1968, Ser. No. 699,458 Claims priority, application Japan, Jan. 27, 1967, 12./5,012, l2/5,013, Ll2/5,014 Int. Cl. H01h 75/12 U.S. Cl. 335-16 7 Claims ABSTRACT OF THE DISCLOSURE A pair of movable contact rods are disposed in parallel relationship at their closed positions and an insulating reset element is movably disposed on those sides of the contact rods remote from the respective contacts. The occurrence of a shortcircuit current generates an electromagnetic repulsion between the contact rods to rotate them in the opposite directions. Then an overcurrent responsive trip mechanism actuates an operating mechanism for switching one of the contact rods between its closed and normally open positions to put the one contact rod in its normally open position. Simultaneously a pivotable holder for holding the one contact rod strikes against the reset element to return the other contact rod to its closed position ready for the succeeding closing operation.

The invention relates to improvements in a circuit interrupter of the type wherein upon the occurrence of a shortcircuit current, an electromagnetic repulsion generated between a pair of movable contact rods is utilized to early separate them from each other thereby to decrease an interruption time as well as giving the current limiting effect.

For circuit interrupters of the type-utilizing such an electromagnetic repulsion to rotate a pair of movable contact rods in the opposite directions, it is necessary to bring the contact rods thus rotated into their normally open positions to which they can be put by the operation of the associated operating or overcurrent responsive trip mechanism for the purpose of being ready for the succeeding closing operation.

Accordingly it is an object of the invention to provide a circuit interrupter of the type wherein upon the occurrence of a shortcircuit current an electromagnetic repulsion generated between a pair of movable contact rods to rotate them in the opposite directions, including improved means for effectively bringing the contact rods thus rotated into their normally open or tripped positions.

According to the invention, there is provided a circuit interrupter comprising a pair of movable contact rods disposed in substantially parallel relationship in the closed position of the interrupter, each of the contact rods being provided at one end with a contact and pivotably mounted at the other end on a pivot pin, spring means individual to each contact rod to normally apply a contact pressure to the association contact, an operating mechanism for switching one of the movable contact rods between its 3,492,609 Patented Jan. 27, 1970 ICC closed and open positions, the other contact rod having only the contacting function, thermally and electromagnetically responsive trip means operatively coupled to the operating mechanism, and a flow of extraordinarily eX- cessive current through the interrupter generating an electromagnetic repulsion on the pair of movable contact rods to rotate the movable contact rods in the opposite directions independently of the trip means thereby to interrupt the current, said contact rods being hel-d in their open positions through reversal of a force of each spring means, characterized in that slightly after the contact rods have been separated from each other the trip means perform the tripping operation to cause the constrained state of the operating mechanism to collapse thereby to automatically bring the pair of contact rods into their positions identical to the normally open positions in which the rods are put through the operation of the trip means.

Preferably the one movable contact rod may be pivotably mounted to a pivotable holder and a reset element of electrically insulating material is movably disposed in slightly spaced relationship between the holder and the other contact rod on those sides thereof remote from the respective contacts. As the constrained state of the operating mechanism collapses due to the operation of the trip means the hold is rotated to push the reset element against the other contact rod to bring it in its tripped position, as well as bringing the one of the Contact rods its tripped position.

The invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIGURE l is an elevational sectional view of a circuit interrupter in its closed position embodying the principles of the invention;

FIGURE 2 is a fragmental side elevational view illustrating the process of moving a pair of movable contact rods from their closed positions to theiropen positions by the action of an electromagnetic repulsion generated between the contact rods due to the occurrence of a shortcircuit current;

FIGURE 3 is a fragmental side elevational view of the movable Contact rods after having been fully opened to interrupt a shortcircuit current;

FIGURE 4 is a view similar to FIGURE 3 but illustrating a pair of movable contact rods in their tripped positions;

FIGURE 5 is a fragmental perspective view of one of the movable contact rods shown in FIGURES 1 to 4 inclusive; and

FIGURE 6` is a plan view of a reset element constructed in accordance with the principles of the invention.

While the invention is applicable to current interrupters having any desired number of poles it will now be described in conjunction with a three pole circuit interrupter with a construction for the central pole thereof illustrated.

Referring now to the drawings and FIGURE 1 in particular, it is seen that an arrangement illustrated cornprises a housing open at one end or the upper end as viewed in the same FIGURE 1, a cover member 12 detachably secured to the housing 10 at the open end, and a pair of movable contact rods 14 and 16 disposed in opposite relationship within the housing 10. The housing and cover member and 12 respectively are moulding of any suitable, electrically insulating material and both the contact rods 14 and 16 are composed of any suitable, electrically conductive material. The first and second contact rods 14 and 16 respectively are provided at one end with a pair of contacts 18 and 20 respectively. When in their closed positions, as shown in FIGURE 1, the contact rods 14 and 16 are positioned in substantially parallel relationship.

The first or upper Contact rod 14 is pivotably mounted by a pin 22 to a Contact holder 24 which is, in turn, pivotably mounted on a pivot pin 26 supported to a fixture block generally designated by the reference numeral 28. The contact holder 24 has fixed at its upper end a connecting rod 30 of any suitable, electrically insulating material to which the contact holders for the outer poles (not shown) are connected. The rst contact rod 14 is adopted to be movable between its closed and normally open positions by an operating mechanism which will be described hereinafter.

The first contact rod 1-4 includes a pair of parallel contact springs 32 having one end anchored to a spring shoe 34 loosely engaging a pin 36 secured to the contact rod 14 at a position located to the left of the pin 22 as viewed in FIGURE 1 and the other ends anchored to a spring shoe 38 loosely engaging a pin 40 secured to the contact holder 24 at a position located to the right of the said pin 22 as viewed in FIGURE 1. With the interrupter put in its closed position, the contact springs 32 serve normally to exert on the first or upper contact 18 a contact pressure under which the contact 18 is maintained in contact with the mating contact 20. However, upon the occurrence of a shortcircuit current flowing though the circuit interrupter to generate an electromagnetic repulsion between the first contact rod 14 and the second contact rod 16 substantially parallel to the upper rod, the contact springs 32 are adapted to move its line of action above the pin 22 to trigger the -first contact rod 14 to its open position independently of an operating mechanism therefor and maintain it in this open position.

As shown in FIGURE 1, a stopper 28a is rigidly secured to a fixture block 28 to determine the open position of the first contact rod 1-4. It is to be noted that the stopper 28a is operatively associated only with that the pole of the circuit interrupter including the fixture block, in the illustrated example, with the central pole of the three pole interrupter, while for each of the other poles a protrusion 12a is disposed on the internal wall surface of the cover member 12 at its position where all the first contact rods, such as 14 are substantially aligned with each other in their open positions. Further, in order to prevent an excessive rotation of the first contact rod 14 about the axis of the pin 22 in the conuterclockwise direction as viewed in FIGURE 1, by the action of the contact springs 32, the contract holder 24 is provided at one and near to the associated contact with an abutment 22a opposite to the pin 36 and the contact holder 24 is also provided at the other end with an overhang 24b for the purpose as will be apparent hereinafter.

The second or lower contact rod 16 is pivotably mounted to a support block 42 by a pivot pin 44 and has a pair of reversing levers 46 disposed in spaced, parallel relationship on both sides thereof. The support block 42 is rigidly secured to the bottom surface of the housing 10. The reversing levers 46 each are pivotably supported at one end near to the contact l on a pivot pin 48 disposed on the support block 42 and are provided on the middle portion with an L-shaped slot 50. The other ends of the reversing levers 46- are connected together by a pin 52 and a pair of spring shoes -54 loosely engage the pin 52 at both ends (see FIGURE 5). A pin 56 extends through the middle portion of the lower contact rod 16 against movement and has secured at both ends a pair of spring shoes 58 to which a pair of contact springs 60' are anchored respectively. The contact springs 60\ have the other ends anchored to the spring shoes 54. To drive the reversing levers 46, the second contact rod 16 further comprises a driving pin 62 movably inserted into the slots 50 on the reversing levers 46.

Like the first contact rod 14, the second contact rod 16 is operatively associated with a stopper 64 disposed on the support block 42 thereby to prevent an excessive rotation of the second contact rod 16 about the axis of the pin 44 in the clockwise direction as viewed in FIG- URE 1.

The second contact rod 16 is electrically connected through a fiexible electrically conductor 66 to an electrical conductor 68 adapted to be electrically connected to a source of electrical power (not shown). The first contact rod 14 is electrically connected through a fiexible conductor 70, and a conductor 72 to an intermediate terminal 74 screw-threaded to the housing 10.

With the second contact rod 16 put in its closed position as shown in FIGURE 1, a straight line passing through both anchoring points where each contact spring 60 is anchored to the respective spring shoes 54 and 58 passes above the axis of the pivot pin 44 for the second contact rod 16 whereby the contact springs 60 tend to rotate the second contact rod 16 about the axis of the pivot pin 44 in the clockwise direction as viewed in FIG- URE 1 thereby to maintain that rod under a predetermined pressure under which the second or lower contact 20 is in engagement with the first or upper contact 18. The said straight line also passes above the axis of the pivot pins 48 for the reversing levers 46 the latter tend to rotate about the axis of the pin 48 in the conuterclockwise direction as viewed in FIGURE 1. Thus the first and second contact rods 14 and 16 respectively are firmly maintained in their closed position when the pivot pin 44 is in engagement with the lowest portion of the L-shaped slot y50 formed on the middle portion of each reversing lever 46.

In summary, the second contact rod 16 tends to be normally rotated about its axis of rotation to have exerted thereon a predetermined contact pressure with respect to the first contact rod 14 by the action of the contact springs 60. However, upon the occurrence of a shortcircuit current yflowing through the circuit interrupter to generate an electromagnetic repulsion between the second contact rod 16 and the first contact rod y14 disposed in substantially parallel thereto, the second contact rod is permitted to be rotated about its axis of rotation in the counterclockwise direction as viewed in FIGURE 1 by the action of the said electromagnetic repulsion until it abuts against the stopper l64.

An H-shaped reset element 76 of any suitable electrically insulating material (see FIGURE 6) is disposed between the overhang 24b of the contact holder 24 and the adjacent end of the second contact rod `16 for the purpose as will be apparent hereinafter. More specifically, the support block 42 has an extension 42a obliquely and upwardly directed from the righthand edge (as viewed in FIGURE 1) toward the overhang 24b of the contact holder 24 and forming a narrow guide passageway 78 with a ramp surface 10a disposed in parallel to the extension 42a of the housing 10. Then the reset element 76 is slidably disposed within the tilted guide passageway 7 8 in such a manner that a pair of leg portions on one side or the upper side (as viewed in FIGURE l) of the H forming a recess 76a are disposed adjacent the overhang 24b on the end of the contact holder 24 while a pair of leg portions on the other side of the H forming recess 76h have interposed therebetween that end of the second contact rod 16. It is noted that the reset element is not physically connected to both the contact holder and the second contact rod.

In order to move the upper contact rod 14 between its closed and normally open or tripped positions and vice versa, the circuit interrupter includes an .operating mechanism generally designated by the reference numeral 80. The operating mechanism 80 comprises an operating handle 82 movably projecting from the cover member 12, a switching lever 84 secured at one end to the operating handle 82 and pivotably mounted at the other end on a stationary pin 86 secured to the Afixture block 28, and a pair of toggle link members 88 and 90 articulated by a toggle pin 92. The mechanism further comprises a pair of tension springs 94 spanned between a spring shoe 84a disposed at that end of the switching lever 84 integrally connected to the operating handle 82 and a spring shoe 92a loosely engaging the toggle pin 92. Thus it will be appreciated that the link members 88 and 90, the toggle pin 92 and the springs 94 from a toggle linkage of the well known construction.

The operating mechanism 80 is operatively coupled to a trip mechanism of the conventional design generally designated by the reference numeral 95. More specifically the link member 90 engages at 96 to a trip lever 98 pivotably mounted at one end on a stationary pin 100 secured to the xture block 28 and engaging at the .other end a primary hook 102. 'I'hen the primary hook 102 engages a secondary hook 104 extending in a casing 106 of any suitable electrically insulating material.

Disposed within the casing 106 is an overcurrent responsive trip mechanism generally designated by the reference numeral 105. The mechanism element cornprises a bimetallic element 108 adapted to be heated with an excessive current flowing through a main conductor 110 electrically connected to the intermediate terminal 74 and an instantaneously tripping electromagnet assembly 112 inductively coupled to the conductor 110. The conductor 110 is adapted to be electrically connected to a load (not shown). The remaining components within the casing 106 will be described in conjunction with the description `of the operation of the circuit interrupter.

The operation of the arrangement illustrated in FIG- URE 1 will now be described.

If the circuit interrupter is desired to be manually moved from its closed position as illustrated in FIGURE 1 to its tripped or normally open position, the operating handle 82 can be thrown to the OFF side or in the righthand direction as viewed in FIGURE l to cause the constrained state of the two toggle link members 88 and 90 to collapse thereby to permit the pivot pin 22 connecting the first contact rod 14 to the holder 24 to be raised. This causes the first contact 18 to be rotated about the axis of the pin 26 in the clockwise direction as viewed in FIGURE 1 to be separated from the second contact 20 until the interrupter reaches its OFF position. The term clockwise or counter clockwise direction used hereinafter means one as viewed in the associated figure.

The circuit interrupter thus open can be again closed by throwing the operating handle 82 to the ON side or reversely from the turning-OFF operation.

It is now assumed that a normal overcurrent flows through the interrupter in its closed position. Under these assumed conditions, that current flows through the conductor 110 to heat it whereby the bimetallic element 108 is deflect to push against a trip adjusting screw 114 facing the same. This causes a trip shaft 116 to be rotated in the clockwise direction to disengage the catch 118 secured to the trip shaft 116 from the secondary hook 104 followed by clockwise rotational movement of the secondary and primary hooks 104 and 102. This causes the primary hook 102 to disengage the trip lever 98. Therefore the constrained state of the two toggle link members 88 and 90 collapses to permit the contact holder member 24 to be rotated about the axis of the pin 26 in the clockwise direction. This rotation of the holder 24 is accompanied by rotational movement of the first contact rod 14 in the same direction as the holder whereby the contact 18 is moved away from the contact 20 resulting in an interruption of the associated circuit.

If an overcurrent having a magnitude equal to 5 to l() times the rating current for the interrupter ows through the latter, the electromagnetic assembly 112 is operated to cause the associated trip rod 120 to rotate the trip shaft 116 in the clockwise direction. Therefore the process as above described is repeated to intermpt the associated circuit.

In the operation ,of manually opening the interrupter or of tripping it in response to the bimetallic element or the electromagnet assembly as above described it is noted that the contact springs 60 permit the second contact rod 16 only to follow the rst contact rod 14 by a very short angular distance suicient to engage the other end of the contact rod 16 with the associated stopper 64. Therefore the second contact rod 16 will remain in its position substantially identical to that illustrated in FIG- URE 1.

It is now assumed that an extraordinarily high current such as a shortcircuit current tlows the circuit interrupter. Under these assumed conditions it will be appreciated that such a current ows through the rst and second contact rods 14 and 16 disposed in substantially parallel relationship, in the opposite directions as shown at the arrows in FIGURE l to generate a strong electromagnetic repulsion between both rods. This causes the contact rods 14 and 16 to be instantaneously and simultaneously rotated in the opposite directions resulting in an interruption of the shortcircuit current. It is to be noted that this interrupting operation is performed independently of the overcurrent responsive trip mechanism 10S. In other words, the holder 24 for holding the first contact rod 14 is maintained in its closed position by means of the operating mechanism whereas the first contact rod 14 is rotated about the axis of the pin 22 in the clockwise direction by the action of the electromagnetic repulsion until the line of action of the contact springs 32 passes upwardly through the pin 22 whereupon its force is reversed in direction. This permits the rst contact rod 14 to be rotated and maintained in its open position as shown in FIGURE 3 where the rod abuts at one end against the stopper 12a. Simultaneously with the initiation of rotation of the rst contact rod 14 as above described, the second contact rod 16 also begins to be rotated about the axis of the pin 44 in the opposite or counterclockwise direction by the action of the electromagnetic repulsion as shown in FIGURE 2. During this rotational movement of the second contact rod 16, the axis of the spring pin S6 has been moved from a position A to B as shown in FIGURE 2 whereupon the contact spring 60 has the line of action coinciding with a line passing through the position B and A of the axis of the spring pins 56 and 48. At the instant that line of the action of the spring 60 has passed downwardly through the axis of the pin 48 for the reversing lever 46 the reversing levers 46 tend to begin to be rotated about the axis of the pin 48 in the clockwise direction. However, a friction around the pin 48 is effective for still holding the spring pin 52 at the position A.

As the second contact rod y16 is further rotated, the axis of the spring pin 56 reaches a position C whereupon the driving pin 62 secured to the second contact rod 16 to drive the reversing levers 46 abuts against the lower edge of the L-shaped slots 50 on the levers to depress them in the clockwise direction. A further rotation of the second contact rod 16 causes the reversing levers 46 to begin to be abruptly rotated in the clockwise direction. As the spring pin 52 for the reversing lever 46 approaches a position D as shown in FIGURE 3 from the position A the line of action of the contact spring 60 rapidly becomes close to the pivot pin 44 for the second contact rod 16 thereby to rapidly decrease the clockwise torque on that contact rod 16 due to the springs 60. This is very effective for decreasing a force opposing the electromagnetic repulsion exerted on the rst and second contact rods.

Then the spring pin 56 for the second contact rod 16 passes through a position G (see FIGURE 3) to a position D while the line of action of the contact spring 60 is moved below the pin 44. Therefore the contact spring 60 exerts on the second contact rod 16 a force tending to rotate it in the counterclockwise direction which force then cooperates with the electromagnetic repulsion as previously described to rapidly move the second contact rod 16 to its position as illustrated in FIGURE 3 resulting in an interruption of the associated circuit.

On the other hand, the spring pin 56 is moved from a position H to a position G as shown in FIGURE 3 while its line of action is moved below the pin 48 whereby the reversing levers 46 are rotated in the clockwise direction about the axis of the pin 48 until it stops at its position as illustrated in the same ligure at which the pin 44 engages the upper edge of the L-shaped slot 50 on each lever 46.

After the rst and second contact rods have performed an automatic interruption operation in the manner as above described, the overcurrent responsive trip mechanism 105 is adapted to be operated with a very small time delay.

As previouslyv described, the operation of the overcurrent responsive trip mechanism 105 is accompanied by collapse of the constrained state of the operating mechanism 80 to cause the toggle link members 88 and 90 to raise the pin 22. This permits the holder 24 to rotate about the axis of the pin 26 in the clockwise direction (FIG- URE 1). At the same time the tirst contact rod 14 is rotated in the counterclockwise direction about that point thereon contacting with the stopper 28 or the protrusion 12a as the case may be. During this rotational movement, the line of action of the contact spring 32 passes downwardly through the pin 22 after which the rst contact rod 14 is downwardly rotated about the axis of the pin 22 and with respect to the holder 24 until the rod returns to its normally open or tripped position as shown in FIG- URE 4.

The clockwise rotational movement of the holder 24 about the axis of the pin 26 due to the operation of the toggle link members 88 and 90 is also accompanied by the overhang or striker 24b on the other end thereof striking against an adjacent end 16a of the second contact rod 16 through the reset element 76. This causes the second contact rod 16 to be rotated about the axis of the pin 44 in the clockwise direction thereby to move the spring pin 56 for the second contact rod from the position D (see FIGURE 3) past a position H whereupon the line of action of the contact springs 60 passes through the axis of the pin 44 to cause the springs 60 to reversely exert its force on the second contact rod 16. This permits the second contact rod 16 to return to its position as illustrated in FIGURE 4 which position coincides with its closed position.

During this returning movement of the second contact rod 1-6, the spring pin 56 reaches the position H (see FIGURE 4) to pass the line of action of the springs 60 through the axis of the pin 48. Substantially simultaneously with this passage, the driving pin 62 abuts against the upper edge of the 'L-shaped slots y50 to raise the reversing levers 46. This causes the reversing levers 46 to rotate in the counterclockwise direction thereby to return the spring pin 52 to a position A to bring the line of action of the springs 60 on the line A-A' until the second contact rod 116 is stopped in its tripped position as illustrated in FIGURE 4.

Therefore the succeeding closing operation can be performed in the conventional manner. Namely the operating handle 82 can be manually thrown to the OFF side to reset the interrupter. Then the handle 82 will be manually brought into the ON position to perform the closing operation.

From the foregoing it will be appreciated that while the present interrupter is of the one point interruption type the first and second contact rods can be separated from each other by a distance larger than the normal separating distance therebetween upon the occurrence of an extraordinarily excessive current such as a shortcircuit current. This establishes a sufficient interruption distance to improve the current limiting effect as in the two point interruption type of circuit interrupters. In addition, after the current limiting effect has been exhibited, -the rst and second contact rods are automatically and substantially simultaneously brought into their normally open or tripped positions, whereby the circuit interrupter is ready for the succeeding closing operation. This contributes to great improvements in performances of the circuit interrupters utilizing an electromagnetic repulsion.

That end 24b of the holder 24 remote from the contact 18 overhangs the reset element 76 to impart to the latter a stroke sucient to return the second contact rod 16 to its closed position. Also the reset element 76 is held separated from the contact rods 14 and 16 and/or holder 24 so as to eifectively utilize an impulse due to the trip operation to return the second Contact rod to its closed position and still be protected from damaging due to such an impulse. On the contrary, the conventional type of circuit interrupter having a reset element physically connected between a rst contact rod or its holder and a second contact rod was disadvantageous in that any impulse due to a trip operation could damage the connection of the reset element and either of the contact rod or its holder as well as complicating the assembling operation.

In order to smoothly and efficiently operate the reset element, the striker 24b and the struck surface of the second moved contact rod 16 are required to be disposed substantially normally to the plane of the reset element 76. With the reset element disposed obliquely to the general bottom surface of the housing, the guide passageway for the reset element must be formed in a complicated manner because the direction of the passageway does not coincide with the standard direction in which the resulting part is removed.

According to the invention, however, the reset element 76 is slidably held within the guide passageway 78 conned by the tilted wall surface 10a of the housing 10 and the extension 42a bent from the support block 42 thereby to be separated from the contact rods and the holder. Therefore the assembling operation is easily performed and the molding process is simplified. Also one Wall of the passageway is composed of the extension of the support block 42 resulting in a small sized circuit interrupter.

Further it will be understood that the second contact rod 16 is given a moment of force equal to the product of a force f provided by the contact springs 60, multiplied by a length of a perpendicular l drawn from the axis of the rotation 44 to the line of action of the contact springs 60. By properly selecting the magnitudes of both the force f and the perpendicular l, the contact rod has applied thereto the requested contact pressure. As shown in FIGURE 2, an electromagnetic repulsion causes rotational movement of the second contact rod 16 to transfer the line of action of the springs 60 from line A-A' to B-B. This prevents the reversing levers 46 from being given the moment of force provided by the contact springs 60. Under these circumstances, a force necessary to start the reversing levers 46 need only be friction around the spring pin 48. In other words, the electromagnetic repulsion exerted on the second contact rod 16 has only a very small portion necessary to rotate the reversing levers 46.

Upon the line of action of the contact springs 60 coinciding with line C-A, the reversing levers 46 begin to be rotated about the axis of the pin 48 in the clockwise direction to move the spring shoes 54 toward the position D'. This causes arapid decrease in the perpendicular l drawn from the axis of rotation 44 to the line of action of the springs 60. Therefore the contact pressure on the second contact rod 16 serving as a moment of rotation in the clockwise direction also rapidly decreases with the result that the second contact rod 16 is easily moved to its open position.

Accordingly, rotational movement of the second contact rod 16 due to the corresponding electromagnetic repulsion is accompanied by the force of the spring 60 for the levers 46 being reversely directed. This causes rotational movement of the reversing levers 46 to displace the spring pin 52 from the position A to the position D. Therefore as the second contact rod 16 is rotated to pass the line of action of the contact springs 60 through line C-A a force exerted in the clockwise direction on the contact rod 16 by the springs is suddenly reversed in direction with the result that the contact rod 16 is stably maintained in its open position. Thus a suicient contact pressure is applied to the second contact rod 16 in the normal contact state and also electromagnetic repulsion exerted on the same rod can be effectively utilized to perform an opening operation.

If a position A anchoring a contact spring is fixed as in the conventional type of circuit interrupters the force of the contact springs 60 begins to be reversed iny direction when the spring pin 56 reaches a position E as shown in FIGURE 4. Therefore, in order to ensure that such a force is reversed in direction, the second contact rod 16 should be rotated to a position E and the moment of force by the springs for the contact rod operating during the electromagnetic repulsion is difficult to attenuate. Also the angle through which the second contact rod can be rotated is required to be large. This causes an increase in depth of the housing 10 and hence in outside the dimension thereof.

Further if the contact spring 60 has one point inimuy ined at the point D' shown in FIGURE 3, the same has the line of action coinciding with the line A-D, this causes a decrease in the length of the perpendicular e drawn from the axis of rotation 44 to the said line of action with the result that a sufficient moment of force supplying a contact pressure on the second contact rod 16 can not lbe produced. If the line of action of the contact .spring 60 is desired to be reversed in direction at the position D' while a sufficient contact pressure is exerted on the second contact rod 16, the anchor point where the spring 60 is anchored should extend to a position F while at the same time the spring and contact rods 60 and 16 respectively increase in length. This not only makes contact assembly large-sized but also the moment of force or the contact pressure can not rapidly decrease after the passage through the position C.

Thus it will be appreciated that the invention also quite effective for rendering the circuit interrupter small sized.

While the invention has been illustrated and described in conjunction with a single preferred embodiment thereof it is to be understood that various changes in the details of construction and the arrangement and combination of parts may be resorted to without departing from the spirit and scope of the invention.

What we claim is:

1` A circuit interrupter comprising a pair of movable contact rods disposed in substantially parallel relationship in the closed position of the interrupter, each of said contact rods being provided at one end with a ,contact and pivotally mounted at the other end on a pivot pin, an operating mechanism for switching one of said movable contact rods between its closed and open positions, thermally and electromagnetically responsive trip means operatively coupled to said operating mechanism, and said contact rods providing a ow of extraordinary excessive current through the interrupter for generating an electromagnetic repulsion Ibetween said pairs of movable Contact rods to rotate the other contact rod independently of said trip means thereby to interrupt the current, the other contact rod when rotated being held in its open position, a pivotable holder on which said one of movable contact rods is pivotably mounted, said holder being provided on that end thereof remote from the associated contact with an overhand, and a reset element of electrically insulating material being movably disposed in spaced relationship `between said overhand on said holder and the adjacent end of the other movable contact rod, whereby slightly after said other contact rod has been separated from said one contact rod, said trip means perform the tripping opperation to cause said operating mechanism to rotate said holder to cause said overhang to strike against the reset element which in turn strikes the end of the other contact rod thereby to return the other contact rod to its initial position.

2. A circuit interrupter as claimed in claim 1 in which a housing is provided for'said interrupter having a tilted wall surface therein, and a support block in said housing for movably supporting the other contact rod, said support block being spaced from said tilted wall surface of the housing to define a guide passageway, and said reset element being slidably disposed in said guide passageway.

3. A circuit interrupter as claimed in claim 1 in which said other Contact rod includes a pivotable reversing lever having a pin thereon and spring means extending from said other contact rod to said pin, the reversing lever being movably mounted on said other contact rod for being moved as said other contact rod is rotated by the electromagnetic repulsion for displacing said pin in a direction to effect early decrease in and reversal of the force applied to the rod by said spring means.

4. A circuit interrupter comprising a pair of movable contact rods disposed in substantially parallel relationship in the closed position of the interrupter, each of said contact rods being provided at one end with a contact and pivotably mounted at the other end on a pivot pin, an operating mechanism for switching one of said movable contact rods between its closed and open positions, thermally and electromagnetically trip means operatively coupled to said operating mechanism, and said contact rods providing a flow of extraordinarily excessive current through the interrupter for generating an electromagnetic repulsion between said pair of movable contact rods to rotate said movable contact rods in the opposite directions independently of said trip means to interrupt the current, said pair of contact rods when rotated being held in their open positions, a pivotable holder on which said one of movable contact rods is pivotably mounted, said holder being provided on that end thereof remote from the associated contact with an overhand, and a reset element of electrically insulating material beinglmovahbly disposed in spaced relationship between said overhang on said holder and the adjacent end of the other movable contact rod, whereby slightly after said contact rods have been separated from each other, said tripl means perform the tripping operation to cause said operating mechanism to rotate said holder to cause said overhang to strike against the reset element which in turn strikes the end of the other contact rod thereby to return the other contact rod to its initial position as well as bringing the one contact rod into its normally open position.

5. A circuit interrupter as claimed in claim 4, wherein a stop is provided on said circuit interrupter for limiting rotational movement of said one contact rod due to the electromagnetic repulsion and responds to the collapse of the constrained state of said operating mechanism to push said one contact rod in a direction opposite to the direction of rotation of the rod due to the electromagnetic repulsion, and spring means associated with said one contact rod and said holder, the push by said stop causing said associated spring means to pass through its dead point to bring said one contact rod into tis tripped position.

6. A circuit interrupter as claimed in claim 4 in which a housing is provided for said interrupter having a tilted wall surface therein, and a support block in said housing for movably supporting the other contact rod, said support block being spaced from said tilted wall surface of 1 1 l 1 2 the housing to dene a guide passageway, and said reset References Cited www element being slidably disposed in said guide passageway. UNITED STATES PATENTS 7. A circuit interrupter as claimed in claim 4 in which said other contact rod includes a pivotable reversing lever 3127488 3/1964 Bodenschatz 335-*16 having a pin thereon and spring means extending from 5 lrlusa Said other contact rod to said pin, the reversing lever being movably mounted on said other contact rod for being FOREIGN PATENTS moved as said other contact rod is rotated by the electro- 1,343,823 10/1963 France.

magnetic repulsion for displacing saidl pin in a direction to effect early decrease in and reversal of the force ap- 10 BERARD A' GILHEANY Primary Exammer plied to the rod by said spring means. H. BROOME, Assistant Examiner 

